Interoffice trunking system



nmy 29, 1924.,

W. T. POWELL INTEROFFICE TRUNKING SYSTEM Juiy 29. 1924. v

W. T. POWELL INTEROFFICE TRUNKING SYSTEM INVENTOR WINFRED T POWELLATTORNEY Filed 1,502,917 W. T. POWELL INTEROFFICE TRUNKING SYSTEM FiledDec. 4, 1920 4 Sheets-Sheet 5 ATTORNEY INVENTOR WIHFRED T POWELL Q@ i ns wa IUI I@ #Wim Fl July 29' 1924- july 29, 1924.

W. T. POWELL INTEROFFICE TRUNKING SYSTEM' Filed Dec.- 4. 1920 4Sheets-Sheet 4 INVENTOR WIHFRED TPOWELL,

BY 9 ATTORNEY and more particularly to systems having a GN TELEPHONEMANUFACTURING CO'MPNY, 0F ROCHESTER, NEW YO CORPORATION OF NEW YORK.

Immersion 'murmure erstma Application filed December e, 1920. Serial No.428,225.

To all whom t may concern.'

Be it known that I, WINFREn T. lownm., a citizen of theUnited States,res1d1ng at ing at different exchanges or oces without the use of the so-called order or instruction telephone c1rcu1ts between the operatorsat Rochester, in the county of Monroe and \said exchan es.'

State of New York, have invented certain `new and useful Improvements inInteroiice Trunking' Systems, of which the following is a full, clear,concise, and exact description. v vThis invention relates to telephonesystems plurality of oiiices or exchanges.

' In former telephone systems, when calls originated in one office for asubscriber at a distant oiice, an' operator known as an A operator,connected the answering end of her cord circuitV to the line of thecalling subscriber and received thedesignation of the wanted line fromthis subscriber. The lAoperator then depressed an oliice key by whichher telephone set was connected to an order` Wire leading to the distantwanted ofiice over which wire the A. operator repeated the number of thewanted subscriber to a B operator at the distant oiice who assigned atrunk for use in completing this call. The A operator then inserted thecalling end of her cord circuit into the jack of the assigned trunk. TheB operator after receiving the number of the wantedv line proceeded totest-this line and, if idle, inserted the calling end of her cordcircuit into the. multiple jack of the wanted line and signalled thewanted subscriber. The use of suchan order wire has resulted in muchdelay and great confusion resulting from the errors due to repeating thenumber thereover.

The present invention has for its purpose the elimination of the orderwire and provides in its stead automatic means for assigning an idletrunk to the distant oilice as `the result of the operation of an oiiicekey and automatic means indicates visually the designation of theautomatically selected trunk, so that the A operator can'connect thecalling end of her cord circuit to the assigned trunk. At thedistantoffice the B operator is informed of the number of the wanted line bymeans of signals variably operated from the A operators position.

The main-feature of this invention is the arrangement of circuits forthe manual interconnection of subscribers lines terminat- Another eatureof this invention is the provision-.of means for automatically assigningan ldle trunk to a wanted exchan e in response tothe operation of a keyindividual -to said oliice and means for automatically indicating thetrunk assigned. Another feature 'of the invention resides 1n the meansfor registering the designation of la wanted line on registering meanslocated at one office and for automatically repeatlng such registrationat a distant oilice to varlably and selectively actuate indicating meansat the distant oice. y

Other features will appear'from the detailed description and appendedclaims. The drawings, with Figures 1, 2 and 3 arranged in the ordernamed and with Fig. 4 placed below Figs. 1 and 2 so that the linesthereof meet, diagrammatically represent a portion of a telephone systememploying the present invention. The circuits, shown on Fig. 1 and atthe left of the heavy dotted lineof Fig. 2 and the circuits of Fig. 4f,representa portion ofthe equipment locatedat one oiice while thatportion of the drawings at 'the right of the heavy dotted line of Fig. 2and those shown in Fig. 3 represent the circuits of a second lofiice. Atthe upper left-hand corner of Fig. 1 there is represented thesub-station circuits of a calling subscriber as well-as a portion of anA operators cord circuit. At the lower lefthand corner of Fig. 1 thereisrepresented a set of ten numerical keys and it is to be understoodthat there is one set of these keys at each operators position. At themiddle and upper portion of the4 sheet of Fig..1 there is represented aswitch referred to as a link finder of which there is one such switchfor each oiice key at each operators position. At the center and rightof FigiJ 1 there is represented a trunk finder switch and a senderfinder switch, the brushes of which are connected together by a circuitreferred toas a link circuit which link is located by the link finder.The trunk finder functions to select an idle one of a group of trunks tothe wante cnice, while the sender finder locates a sender of the commonoup of senders which has been preselected y a preselector switch shownat the bottom of Fig. 1. At the lower right-hand corner of Fig. 1 andthe left-hand corner of Fig. 2 there is represented a progressivelymovable switch, herein referred toas a sender switch, while in the lowerpart of Fig. 1 and in Fig. 4 there are shown the relay registers forstoring up the designation of the thousands, hundreds, tens, units andstations designations. At the upper left-hand corner of Fig. 2 there isshown a portion of an indicating board common to a plurality ofoperators positions and of which there is one such board for each officereached from the first mentioned ofiice. On this board there are locateda plurality of lamps for indicating the tens and units designation of anautomatically assigned trunk to a Wanted oiiice. At the center of Fig. 2there appears a progressively movable switch, lherein referred to as areceiver switch and at the upper portion of Figs. 2 and 3, there appearsa representation of the B operators cord circuit, while at the lowerpart of Figs. 2 and 3 there is represented the line indicator lamps andthe relays for controlling the same.

It will be understood that the number of trunks such as that shown atthe upper portion of Figs. 1 and 2 will 'vary in accordance with thetraiiic between the various offices, similarly the number of senders forthe ilse of all A operators positions located at the same oiiice willdepend on the number of simultaneous calls therefrom.

It is believed that the invention will best be understood by describingthe method of operation employed in establishing a telephone connectionfrom the sub-station of a calling subscriber indicated at A to thesub-station of a wanted subscriber, "B, whose telephone line terminatesin another exchange herein designated Main. When the calling subscriberremoves his receiver from its switch hook, the line relay 5 is operatedin the well known manner to light the line lamp 6. The A operator theninserts the plug 7 into the multiple jack 8 of the calling line which iseffective to operate the cut-off relay 9 and this relay in turndisconnects the line relay 5 to extinguish the line lamp 6. Theanswering supervisory relay 10 of the cord circuit taken for use is alsooperated in this portion of the operators cord circuit which is notshown complete, since it may be of any well known arrangment. The Aoperators telephone set (not shown) is then connected to the callingline, either manually by listening key 11, as indicated, or it may beconnected to the calling line through the operation of well knownautomatic connecting means so that the operator may inquire thedesignation of the wanted subscribers line.

For purposes of this description, it has armatures as the result of theclosure of this circuit and closes a locking circuit for itself fromground at its inner upper armature and front contact, its lower winding,continuity spring and contact of relay 18, contacts of wipe-out key 19,winding of relay 14, armature, back contact and winding of the motormagnet of the sender preselector to grounded battery. y

The motor magnet will not operate in series with the mentioned relays.but the relay 14 is actuated and the relay 17 isheld operated in thelast described circuit. As soon as relay 14 operates, it closes multipleactuating circuits for relay 21 which con nects the operators numericalkey set to the preselected sender and the key set lamp 22 whichindicates this connection. These circuits extend from grounded battery,winding of relay 21, lower front contact and armature of relay 14, backcontact and armature of relay 13 to ground. The lighting of the key setlamp 22 indicates to the operator that the digits keys appearing at thelower left-hand corner of Figure 1 may he operated in accordance withthe designation of the wanted number. The operation of relay 14 alsocloses a circuit for actuating relays 23 and 25 in series. this circuitextending from ground. winding of relay 23. upper front contact andarmature ot relay 14. sender preselector brush 24 and winding of' relay25 to grounded battery. The operation of relay 25 closes at its armatureand front contact, a circuit from ground over conduo tor 31, armatureand back contacts of relay 32 and the switching relays 27, 28. 29 and ofthe stations units` tens and hundreds registers, over conductor 33.right-hand winding of the thousands register switching relay 26,conductor 34, to grounded battery for actuating relay 26.

When relay 17 attracts itsl armatures, the operating and test circuitsof the link finder. individual to 'the group of trunks assigned to theMain oiiice, are closed. The operating circuit for the link finder isclosed from grounded battery. resistance, armature and cont-act 124 ofrelay 17, back contact. armature and winding of motor magnet 42,continuity spring and back contact of relay 40 to ground, and advancesthe link finder brushes until an idle link circuit is reached. whereuponthe test circuit is completed from.

. ot` an idle link circuit.

neef/reir ground at the make-busy relay 36, righthand back contact andarmature of relay 37, conductor 38, back contact and armature of relay39. test brush 35, right-hand winding ot' relay 40, front-contact andarmature of relay 17. conductor 41, resistance to gounded battery. Thislast named circ-uit is effective to shunt the motor magnet 42 of thelink finder which then stops its brushes 43, 44, 35 and 45 in engagementwith the terminals erated in the last described circuit and closes alocking circuit for vitself from ground, winding of relay 39, holdingbrush 45 of the link finder, left-hand high resistance winding of relay40, its innerarmatune and continuity spring, winding of the motor magnet42, its armature and back contact, lower frontl Contact 124 and armatureof relay 17, conductor 41and resistance to grounded battery, Theoperation of relay 39 renders the chosen link unselectable.

'Also when the relay 39 is operated, it closes operating circuits forthe trunk finder switch and for the sender finder switch, the

first of these switches being advanced in a circuit completed fromground, up er contact and continuity spring of relay 4 winding of motormagnet 48 of the trunk finder, its armature and back contact, innerfront contacty and armature of relay 39, outer back contact and armatureof relay 37, through the resistance to grounded battery. vUnder thecontrol of this circuit, the trunk finder t switch advances its brushes50, 51, 52, 53

and 54. until its test brush 54 engages a test terminal having groundpotential applied at the left-hand armature and back contact of relay 55whereupon the circuit is closed through the lower winding of relay 47,front Contact, and armature of relay 39, back contact and armature ofrelay 37, resistance to grounded battery.

, This circuit is effective to stop the trunk finder and also toenergize the relay 47 which thereupon closes a locking circuit foritself from ground at the armature and back contact of a relay similarto 55 at another trunk over the multiple connection 218, left-handwinding of relay 55, holding brush 53, high resistance winding of relay47, its upper armature and continuity spring, winding of motor magnet48, its armature and back contact, to grounded battery, through thecontacts and armatures of relays 39 and 37, as previously described.

In the event that all the trunks leading from the terminals of a trunkfinde-r are busy, all the relays such as 55 of this group of trunks willbe operated, thus removing the short-circuit from the common makebusyrelay 36, permitting this last named relay to operate and disconnect thestopping ground potential from all the test terminals at the link finderswitches, thus The relay 40 is oppreventing an link finder fromselecting a linkV circuit aving no available outgoing trunk at the trunkfinder switch.

The operating circuit of the sender finder is traceable from groundedbattery through the resistance, outer right-hand armature and frontcontact of relay 39, back contact,

armature and windin of the motor magnet 56 of the sender fin er,continuity spring and contact of relay 57 to ground. This last describedcircuit causes the motor magnet 56 of 'the' sender finderv to advancebrushes 58,' 59, 60, 61 and 62 of this switch until it reaches the samesender to which the key set is connected by 'way of the pre-` selectorswitch. At this time, ground at the armature and front contact of relay23 is extended throughy brush 64 of the sender preselector, test brush62 of the sender finder, upper winding of relay 57, outer righthandfront contact and armature of relay 39 and resistance to groundedbattery. The relay 57 is thus actuated and at its lower contact andcontinuit spring opensv the energizing circuit Iof t e motor magnet 56and instead closes a circuit from grounded battery, outer armature andfront contact of' relay 37, back contact armature and Winding of motormagnet 56, continuity sprin `and armature of relay 57, through the higresistance Winding of this relay, holding brush 61 of the sender inder,winding of relay 65 to ground. The operation of relay 65 closes anactuating circuit for relay 25l lattracted its armatures to connect theset of numerical keys to the registers. The apparatus is now incondition to receive the designation of the wanted telephone line. Sinceit has been assumed that the wanted numberis 7764-R, the operator willthereupon depress the No.7 numerical key of the key set to close acircuit from ground, spring contacts 75, conductor 76, innermost lowerarmature and front contact of relay 21, brush 77 of the senderpreselector switch, left-hand armature and front contact of relay 26,lower winding of the sensitive relay 78 and lower winding of themarginal relay 79, winding of relay 80, to grounded battery. Relays 78,79 and 80 all operate in series and the first two mentioned relays closelocking circuits through their upper lil windings, front contacts andarmatures, through conductor 31, front contact and armature of relay 25,to ground. The o eration of relay 80 closes an energizing circuit forthe relay 81 from battery, through its right-hand winding and throughthe armature and continuity spring of relay 80, to ground. Relay 81 thencloses a locking circuit through the left Winding of relay 26 togrounded battery over conductor 34. When the No. 7 key is released,relay 80 retracts its armature and thereby closes a holding circuit forrelay 81 which extends from ground at the continuity spring and contactof relay 80, left-hand winding, front contact and armature of relay 81,armature 82 and front contact of relay 26, right-hand winding of thehundreds register switching relay 30 to grounded battery for operatingthis relay. The primary locking circuit for relay 30 extends fromgrounded battery, left-hand winding, front contact and armature of relay30, conductor 83, to ground at armature and contact of relay 81. Therelay 30 on operating closes a second locking circuit for itself fromgrounded battery, through its right-hand winding, front contact andarmature and through the back contacts and armature of relays 29, 28, 27and 32, over conductor 31 to the holding ground at the armature andfront contact of relay 25. This last described circuit also is effectiveto short-circuit the left-hand winding of relay 81, so that thislastnamed relay deenergizes and retracts its armatures. Thedeenergization of relay 81 opens the holding circuit for the thousandsregister switching relay 26 which extended through the left-handwinding, front contact and armature, to ground at relay 81. Theswitching relay 26 thereupon deenergizes and disconnects the thousandsregister relays from the control of the numerical key set, butl relay 30has already eX- tended this key set to the four relays of the hundredsregister. Since the hundreds digit of the wanted number is 7, theoperator again depresses key No. 7 to close a circuit from ground, keycontactl 75, conductor 76, inner lower armature and front contact ofrelay 21, sender preselector brush 77, conductor 93, armature 86 andfront contact of relay 30, lower windings of sensitive relay 87 andmarginal relay 88, winding of relay 80. to grounded battery. Relays 87,88 and 80 are operated and the register relays 87 and 88 close lockingcircuits through their upper windings, front contacts and armatures overconductor 31, to ground at the contact and armature of relay 25. Whenkey No. 7 is released, relay 80 deenergizes and again completes alocking circuit for relay 81 (which was energized simultaneously withrelay 80) from ground at the continuity spring and contact of relay 80,

winding of relay 81, its front contact and armature, armature 82 andback contact of switching relay 26, armature 88 and front contact ofrelay 30, right-hand Winding of thel tens register switching relay 29 togrounded battery. The switching relay 29 attracts its armatures andcloses two locking circuits for itself; the first extended from groundedbattery, through its lefthand winding, front contact and armature,conductor 83, outer armature and front contact of relay 81 to ground,which circuit insures that the relay 29 will be held by its secondlocking circuit including its righthand winding, front contact andarmature through the back contacts and armatures of relays 28, 27 and 32over conductor 31, to ground. The tens register is now in condition tobeA adjusted in accordance with the tens digit of the wanted numberwhich in the case assumed is 6. The operator thereupon depresses key 6to close one circuit from ground, through the resistance, key contacts90, conductor 76, innermost armature and front contact of relay 21,sender preselector brush 77, conductor 93, armature 94 and front contactof relay 29, lower windings of the sensitive register relay 95 andmarginal relay 96, through the winding of relay 80, to grounded battery.The sensitive relay 95 and the relay 80 are energized in this seriescircuit but the marginal relay 96 remains inert. On the operation ofrelay 95, a locking circuit is closed through its upper winding, frontcontact and armature, over conductor 31 to the holding ground. When theoperator depresses numerical key No. 6, a second circuit is closed fromground resistance, key contacts 90, conductor 91, lowermost armature andfront contact of relay 21, sender preselector brush 92, conductor 85,outermost armature and front contact of the tens switching relay 29,upper windings of the sensitive re- -lay 227 and marginal relay 228,conductor 103, to grounded battery through the winding of relay 80. Themarginal relay 228 does not operate in the circuit but the sensitiverelay 227 is energized and closes a locking circuit for itself throughits lower winding, front contact and armature to the holding ground ofconductor 31. On the energization of relay 80, an operating circuit isclosed through the right-hand winding of relay 81 for operating it. Thiscloses a temporary holding circuit from ground at the outer frontcontact and armature of relay 81, conductor 83, armature, front contactand left-hand winding of relay 29, to grounded battery over conductor34. This circuit insures that the relay 29 will remain energized, untilits locking circuit through its right-hand winding is completed. Whenthe numerical key No. 6 is released, relay 80 deenergizes and a lockingcircuit is closed through the left-hand winding ofrelay 81,

y the right-hand winding of this relay, the relay 81 is againshort-circuited and the units register .is in condition to be adjustedin accordance with the units digit of the wanted number which, in thisinstance, is No. 4. The operator now depresses numerical key N o. 4 andthereby closes a circuit from ground, through the contacts 98, conductor99, upper armature and front contact of relay 21, sender preselectorbrush 100, conductor 101, right-hand armature and front contactof relay28, lower windin of marginal relay 102, conductor 103, wlnding of relay80, to grounded battery. On the release of the No. 4 numerical key, thestations register switchin relay 27 is energized and locked operated 1nmanner similar to the actuation of the other switching relays and theunits re ister switchin relay 28 deenergizes and t e relay 81 o Flg. 1is short-circuited, as previously described. Since the wanted subscriberis party R, the operator presses the party key for this party which, inthis instance, is the same as the numerical key for No. 3. On theoperation of this key a circuit is closed from ground, resistance, keycontacts 104, conductor 76, innermost armature and front contact ofrelay 21, sender preselector brush 77, conduc tor 93, armature 105 andfront contact of switching relay 27, lower windings of sensitive relay165 and marginal relay 226, through conductor 103 and Winding of relay80 to grounded battery. r1`he marginal relay 226 does not operate inseries with the mentioned resistance, but the sensitive relay 165attracts its armatures and locks itself operatedthrough its upperwinding, front contactand armature to ground, over conductor 31.

1n the event that the wanted number is an individual line without theparty letter, the operation of the start key 108 functions the same asoperating the key for party J which-key operates relay 106 of thestations register. This will indicate to the B operator that station Jis wanted and, when she operates the ringing key for party vJ, 33 cycleringing current is selected which will signal the individual line. Itwill thus be seen that,when the kstart key is operated on a call for aparty line other than party J, relay 106 will not be operated because ofthe fact that the operation and release of a key to operate a relay ofthe stationls register releases the relay 27 so that any subse uentoperation of the numerical keys wil not te ect the adjustment of any ofthe regisers.

After the A operator has adjusted the numerlcal registers in accordancewith the designation of the wanted number, the start key 108 isdepressed and held until the indicator pilot lamp 109 of Fig. 1 islighted.

The lighting of the lamp 109 is effected by Y the closure of the circuitincluding the conductor 111 which is closed at the left-hand armatureand front contact of rela 110 Which relay is operated as will now edescribed.. On the depression of the start key, a circuit is closed fromgrounded battery, resistance, upper contact of start key 108, winding ofrelay 18, conductor 112,' outer left-hand armature and front contact ofrelay 40 (which it will be remembered was energized as soon as the linkfinder of Fi l .had seized an idle link), left-hand windln of relay 110,through the back contacts an continulty springs of other relays similarto relay 110 of other positions located at link nders operated from theMain office keys. It will thus be seen that if no other operator has astart key similar to 108 depressed on a call to the Main office, relay110 will opcrate and lock itself operated through its continuity spring,armature and right-hand wmdmg and uppermost armature and front contactof rela 17. Relay 110 on attracting its armatures reaks the seriesground circuit which is arranged so that no other operator can disturbthe connection under completion until the operator in attendance on thepresent call has released her start key and then onl one operator cane'ect the operation of t e relay corresponding to 110 at anotherposition. When 110 attracts its armatures .in the manner described, itcloses a circuit to light the indicator pilot lamp as previouslydescribed which informs the operator that the cord circuit in herposition is associated with the common indicator board shown in theupper left-hand corner of Fig. 2. Relay 110 at this time also closes acircuit to o erate relay 113 which circuit is traceable rom groundedbattery, winding of this relay, conductor 114, link iinder brush 43,left-hand front contact and armature of relay 110 to ground. Relay 113is thus operated and closes an actuating circuit for relay 37 extendingfrom grounded battery, -ri ht-hand winding of this relay, innermost rontcontact and armature of relay 113, u permost front contact and armatureof re ay 47, armaturev and back contact of relay 115, trunk finder brush52, windin or' sensitive relay 116", winding of margina relay 117, frontcontact and armature of relay 55 (which was energized in series withrelay 47) to ground. The operation of relay 117 is eective to light thetens and units lamps on the indicator board to indicate the trunkdesignation of the trunk assigned for use, into the jack of which 118the operator will insert the calling plug 119 of her cord circuit. Inthe drawlng this trunk is shown as trunk No. 12 and the marginal relay117 completes circuits to light the tens lamp 120 and the unitslamp-121. On receiving this number indication, the operator inserts thecalling plug 119 of the cord circuit taken for use into the jack 118 andreleases the start key 108 which extinguishes the lamps on the commonindicator board as will be pointed out. When the start key 108 isreleased, at its upper contacts it opens thel circuit which has beenlocking the relay 17 operated and since the relay 18 is slow to releaseits armature, the original locking circuit of lrelay 17 is open at thecontinuity spring and contact of rela 18. Therefore the relay 17deenergizes an as soon as it retracts its ar- -matures, it opens thelocking circuit Jfor relay 110 whic extended through the uppermost frontcontact and armature of relay 17 and relay 110 on deenergization causesrela 113 to release its armatures. Also at the iower armature andcontact 124 of relay 17, the energizing circuit of relay 39 isinterrupted and th1s circuit releases its armatures and thereby causesthe dee'nergization of relay 47. The operators circuits and the linkfinder which has just been in use are now in normal condition and inreadiness for use on a subsequent call.

When relay 113 of the trunk finder is released, as above described, thelow resistance Winding of relay 37 is disconnected from thev windings ofthe sensitive relay 116 and marginal relay 117 of the trunk circuit.Relay 37 and relay 116, however, do not deenergize because of a circuitextending from grounded battery through both windings in series of relay37, its inner front contact and armature, armature and back contact ofrelay 115, trunk nder brush 52, relays 116 and 117, to ground at thefront contact and armature of relay 55. Because of the high resistancewinding of relay 37 now included in this circuit, the marginal relay 117deenergizes and extinguishes the lamps on the indicator board whlchhavebeen lighted for indicatin the trunk assignment. Relay 37 now ho ds thetrunk finder busy and also causes the sensitive relay 116 of the trunkand the lrelay 57 of the sender finder to remain operated. Since thecalling plug 119 of the A operators cord circuit is in enga ement withthe jack contacts 118 of trunk o. 12, the relay shown at the right ofFig. 1 is held operated from grounded battery, through the sleevecontacts of the mentioned plug and jack winding of the relay 55 toground over conductor 218, at the armature and back contact of a relaysimilar to 55 at another trunk of this group. Relay 55 while operated,indicates that trunk No. 12 is in use.

When the common set of numerical keys of an operators position such asthat shown at the lower left-hand corner o f Fig. 1 is released, it isimmediately connected to an idle register sender of the common group ofregister senders ofy which there are only enough provided to handlesimultaneously calls to all offices, during the interval thattransp'ires between the depression of the otlice key by the A operator,until the number indication has'been transferred to the \B operatorsnumber indicator. It will be recalled that when relay 18 was energizedat the close of the operation fof the numerical keys, relay 14deenergized. rlhis closed an energizing circuit for relay 13 as lon aspreselector brush 24 tested test contacts laving a busy potentialapplied atthe armature and front contacts of relays similar to relay atengaged register senders. With relay 13 operate motor magnet 20 advancesthe preselector brush to select an idle register sender.

As soon as the number has been set up on the ke set in the mannerindicated and when t e start key is operated, the operator receives thetrunk assignment by the lighting of trunk indicator lamps, such as 120and 121 on the common indicator board and thus it is not necessary forthis trunk assignment to be transmitted to the A operator from the Boperators position over an order wire.

It will be understood that the registers of a register sender remainadjusted to store up the number designation of the wanted number untilthe B operator is -in readiness to receive this indication on the numberindicator shown at the right of Fi 2 and at the lower part of Fig. 3,thus 1t is not necessary for the A operator to repeat the wanted numberto the B operator. It will be pointed out in this description how thewanted number is displayed on the indicator at the B position until theB operator is in readiness to attend to the call and it remains as avisual indication of the wanted number until the B operator extinguishesthe operated number indicating lamps either by operating a commonrelease key 125 or by insertin the plug 126 into a multiple jack 127 oft e wanted line. A

The B operator receives the indication of the wanted line over selectedtrunk No. 12 when the A operator depresses the start key 108 of Fig. 1,which operation closes a circuit from ground, winding of relay 129 ofFig. 2, sender brush 130 in its normal position, conductor 131, senderfinder brush 60, lowermost front contact and armature of relay 57,conductor 132, trunk inder brush 50, uppermost front contact andarmature of the sender switch into its zero position.

vswitch to advance it into position 1.

This circuit is traceable from the armature and front contact of relay129, sender brush 136, conductor137, back contact, armature and windingof motor magnet 126 of the sender switch, to grounded battery. Theoperation of relay 135 closes a circuit for operating the slow releasingrelay 138 and this relay connects the lamp 139 in circuit with theintermittently closed contacts 140 of the common flashing device, thiscircuit being traced from grounded battery, through the lamp 139, innerarmature and front contact of relay 138, armature and back contact ofrelay 141, conductor 142, contacts of the flasher 140, to ground. Onnoting that lamp 139 is intermittently lighted, the operator presses theassignment key 143 and thereby closes a circuit for operating the relay134 which extends from ground, through the contacts of this key, upperwinding of relay 134, conductor 144, receiver brush 145 in its normalposition, armature, back contact and winding of the motor magnet 1,46,to grounded battery. This circuit is eHective to cause the energizationof the relay 134 which thereupon closes a locking circuit for itselffrom grounded battery, contacts on the release key 125, conductor 147,winding of relay 148, conductor 149, lower winding, front contact andarmature of relay 134, conductor 150, to ground at the inner armatureand back contact of relay 151. The guard lamp 152 is energized inmultiple with this last described circuit. Relay 148 is operated in thelocking circuit just described and closes an operating circuit for themotor magnet 146 of the receiver circuit is traceable from groundedbattery, winding of motor magnet 146, its back contact and armature,receiver brush 145 in its normal position, right-hand front contact andarmature of relay 148 to ground. As soon as the receiver switch movesout of its normal position, no other relay such as 134 can be operatedby falsely pressing another assignment key, because the batterypotential through the winding of the motor magnet 146 is removed fromthese relays when the receiver switch leaves its normal position. Theoperation of relay 134 also disconnects the tip and ring conductors 133and 153 from the B operators cord circuit and connects these conductorsto the brushes 154 and 155 of the receiver switch. The opening @ofconductor 133 causes relay 135 to deenergize and also effects thedenergization of This that this operator can depressthe stations` keywhile the remainder of the wanted number designation is being received.Since the receiver and sender switches step alternately and since eachswitch must complete twentyone steps to effect the number designation atthe registers of the B operators position, the total number of stepstaken by both of these switches 1s forty-two and will require about onesecond of time to display the'complete deslgnation of the wanted line,after the B operator presses the assignment key 143.

It Will be remembered that the sender and recelver switches are each inposition 1 so that a circuit is now extended from ground, winding ofrelay 160, conductor 161, brush 154, uppermost front contact andarmature 0f relay 134, tip conductor 133 of the selected trunk,uppermost armature and front contact of relay 116, tru-nk finder brush50, conductor 132,- lowermost armature and front contact of relay 57,sender finder brush 60, conductor 131, brush 130 in position 1,conductor 162, upper front contact of relay 106, but, since relay 106was not opera-ted, this circuit is incomplete at this point. Aft thistime a circuit is closed from ground, through the low resistance windingof relay 166, brush 155, inner upper armature and front contact of relay134, ring conductor 153, of the trunk selected` inner upper armature andfront 'Contact of relay 116, trunk finder brush 51, conductor .167,armature and front contact of relay 5T, sender finder brush 59, brush168 in position 1, through both windings in series of relay 169, togrounded battery. The relay 166 will not operate in series with the highand loW resistance windings of relay 169 but this last mentioned relaywill be energized to close a circuit for advancing the. sender switch toposition 2. This circuitl may be traced from grounded battery, windingof the motor magnet 126 of the sender switch, armature and back con-tactof this magnet, conductor 137, b-rush 136 in position 1, fron-t contactand arma-ture of relay 169, t0 ground. In position 2 of the senderswitch, the low resistance winding of relay 169 alone is connectedthrough brush 168 and sender finder brush 59 to the ring conductor 153of the selected trunk through brush 155 and low resistance winding ofthe relay eov 166 to ground. Relay 166 is energized in this circuit andcauses the motor magnet 146 of the receiver switch to be advanced in acircuit traceable from grounded battery, winding`v back contact andarmature of this magnet. brush 171 in position 1, front contact audarmature of relay 166, to ground. In position 2 of the receiver switch,the relay 192 is connected tothe stations register of the A oilice overa circuit extending from grounded battery, conductor 231. winding ofrelay 192, conductor 232, receiver brush 154 in its second position,uppermost front Contact and armature of relay 134, tip conductor 133 ofthe selected trunk, upper armature and front contact of relay 116, trunkfinder brush 50` conductor 132, lowermost armature and front contact ofrelay 57 sender finder brush 60, conductor 131, sender switch brush 130in its second position, conductor 234, but this circuitv is in complete.at the upper front contact and armature of relay 107 so that relay 1921s not operated. lVhile the. receiver switch is in position 2, the highresistance winding of relay 166 is connected in series with the lowresistance windingof relay 169 at the sender switch, causing this lastmentioned relay to deenergize while the relay 166 at the receiver switchremains operated. The sender switch is now advanced to position 3 in acircuit traceable from grounded battery, winding of its motor magnet126, ar-

f mature and back contact of this magnet,

conductor 137, brush 136, conductor 170, back Contact and armature ofrelay 169, to ground. In position 3 of the sender switch a circuit isclosed from ground through both windings of relay 173, brush 168 of thesender switch, brush 59 of the sender finder switch. middle contact andarmature of relay 57 conductor 167, trunk nder brush 51, inner frontcontact and armature of relay 116 over ring conductor 153 of the trunk,inner armature and front contact of relay 134` receiver switch brush 155in its second position, through both high and low resistance windings ofrelay 166, to ground. The relay 166 deenergizes and thereby completes acircuit for the motor magnet 146 to advance the receiver switch intoposition 3. As soon as the receiver switch enters this position, acircuit is closed for operating relay 193, extending from ground,winding of' this relay. conductor 235, receiver switch brush 154.uppermost front contact and armature of relay 134. tip` conductor 133 ofthe selected trunk, uppermost, armature and front contact of relay 116,trunk finder brush 50, conductor 132, lowermost armature and frontContact of relay 57, sender finder brush 60, conductor 131, senderswitch brush 130, conductor 236, lowermost front contact and armature ofrelay 165, resistance to grounded battery. The relay 193,

also closed from battery, through the low resistance winding of relay172, brush 155, over the circu-it previously described to brush 16S ofthe sender switch in position 3, through the high and low resista-ncewindings of relay 173, to ground. Relay 173 is operated in this circuitan-d at its front contact and armature closes an operating circuit forthe motor magnet'126which advances the sender switch intol position 4.In this position, the low resistance winding of relay 173 is connectedto trunk conductor 153 to energize relay 172, which closes an operatingcircuit for magnet 146 of the receiver switch for advancing this switchinto position 4. The high resistance winding of relay 172 is nowincluded in the circuit eX- tending over` trunk conductor 153, andthrough the low resist-ance winding 0f relay 173 which causes this lastnamed relay to deenergize and advance the sender switch into position 5,where battery potential is extended through both windings of relay 169,brush 168, sender finder brush 59, front contact and armature 0f relay57, conductor 167 trunk finder brush 51, front. contact and armature ofrelay 116, conductor 153, inner armature and front contact of relay 134,lbrush 155, through both windings of relay 172, t0 battery potential.This causes relay 172 to deenergize and advance the receiver switch intoposition 5. This alternate operation of the sender and receiver switchescontinues, until both-switches are advanced to position 21.

It will be seen that the brush 154 of the receiver connects the twentyrelays of the indicator successively to the tip conductor 133 of theselected trunk as the receiver switch advances its brushes throughposition 1 to 20, inclusive. The brush 130 of the sender switch connectsthe mentioned tip conductor 133 of the selected trunk vsuccessively tocorresponding relays of the registers and the register relays which havebeen operated in response to the depression of the numerical keys willclose circuits to operate and lock corresponding relays at the indicatorat the wanted ofiice. It should be noted that the relays of the registersender and of the indicating device are so connected to the variouscontacts of the sender switch and receiver switch, that as theseswitches are advanced, current is reversed in the signaling circuit ineach succeeding positions of these switches. In this way the overlap,when the sender switch moves, will not falsely operate a relay at thewanted office.

In the case assumed, relays A, B, E, F, I,

` K, N and G of the sender registers were locked operated in res onse tothe depression of the proper keys o the numerical key set and, after theoperation of the sender and receiver switches has taken place,corresponding relays will be ener 'zed and locked operated in thereceiver of t e dlstant oilice. With these last mentioned relaysoperated, circuits can readily be traced for ighting only the stationslamp R, thousands lamp No. 7, hundreds lamp N o. 7, tens lamp No. 6 andlunits lamp No. 4.

When the sender switch reaches osition 21, a circuit is closed fromgroun ed battery, winding of magnet 126, conductor 137, brush 136,conductor 180, sender finder 'brush 58, upper armature and front contactof relay 57, winding of relay 115 to ground. The magnet 126 remainsinert, but the rela 115 is operated to open the operating circult of therelay 116 of the trunk and the o erating circuit of relay 37 of thetrunkv der. Relay 37 in turn opens the holding circuit of relay 57 ofthe sender finder swltch and the relay 65 of the sender which rela inturn causes relay 25 to deenergize. en relay 25 retracts its armature,it closes a circuit from ground, through the sender switch brush 128,conductor 127, back contact, armature and winding of motor magnet 126 togrounded battery and thereby advances the sender switch into its normalposition, while the relay 25 at its front contact o ens the lockingcircuit which has been vhol ing the actuated relays of the registers inoperated position. The trunk finder and the sender finder remain in theposition last used.

After the lighting of the indicator lamps at the distant oiiice, the Boperator notes the designation of the wanted l1ne and tests the multipleof the wanted line in the well known manner and, if this line is idle,inserts the plug 126 into the multiple jack 127 of this line. This lastoperation actuates the sleeve relay 151 which thereupon opens theconductor 150 by which the relay 134 and relay 148 have been heldoperated. Relay 134 deenergizes and extends the conductors 133 and 153of the selected trunk through the windings of the repeating coil of theB operators cord circuit. The relay 148 upon deenergizing closes acircuit from ground, through its armature and back contact, brush 145 ofthe receiver switch, armature, back contact and winding of the motormagnet 146 to grounded battery which circuit is effective to advance thereceiver switch to its normal position.

The B operator, after inserting the plu 126 into the multiple jack 127of the wante line, depresses the party key 190 for connecting ringingcurrent of the proper frequency to signal the wanted subscribersstation. The depression of key 190 also closes contacts 241 which closea circuit for the erated in multiple-with the last described circuitthrough its continuity spring and 'contact and, when operated, closes alocking circuitfor itself through its continuityv spring and armature.As soon as the rela 242 is operated, it closes a ringing circuit fromthe source of current through the de pressed party key 190 and in serieslthrough the back contacts of keys 189 and 188, con# ductor 243, lowerfront contact and armature of relay 138, winding of trip relay 244,upper front contact and armature of ringing relay 242 through the lowerside of the operators cord circuit and called line in series, throughthe tuned ringer at the B subscribers station over the upper side ofthis line and the operators cord circuit in series to ground at theuppermost armature and front contacts of ringing relay 242. When thecalled party responds, the trip relay 244 attracts its armature toshort-circuit the ringing relay 242 which thereupon opens its lockingcircuit and remains inert to pre.- vent inadvertent reapplication ofsignalling current on this connection. Also, when the ringing relay 242retracts its armatures, it completes a circuit for the supervisory relay245 through which talking battery 1s supplied to the wanted subscriber.The supervisory relay is maintained operated in this circuit and closesa circuit to apply talking battery to the answering end of the Boperators cord circuit through lthe winding of relay 135 and impedancecoil 246.

It has not been deemed necessary to fully disclose the details of theoperators cord circuits by which supervision is obtained since theseoperations take place in the same manner. as in multi-oiiice telephonesys-` tems now in use. It will be sufficient to understand that at thetermination of the conversation, proper signals will be displayed to theA and B operators who thereupon manually restore the cord circuits whichhave been in use.

It should be pointed out that the B operator can increase the speed ofcompleting connect-ions at her position by operating the common releasekey 125, as soon as she has noted the designation of the wanted lineinstead of waiting for the release operation of the receiver relayregisters to be effected by inserting the plug 126 into the multiplejack 127.

By arranging the incoming trunk circuit with a so-called automatic busytest arrangement, that is, an arrangement wherein the operator does nothave to test the mul tiple of a wanted line but simply lnserts. the plugof lier cord circuit into a multiple Jack of this line whereuponautom'atlc means completes the connection, if the wanted line is idle,and prevents the completion of this connection, if the wanted line isengaged, the B operator need not be provided' with a telephone set.While in this disclosure manual party keys have been disclosed forselecting the current of proper frequency for selecting. wanted stationson a party line, it will be understood that the system herein disclosedwill be equally effective, if the signalling current is selectedautomatically.

What is claimed is:

l. In a telephone system, an operators position, telephone linesterminating in said position, a second operators position, other linesterminating thereat, trunk circuits connecting said positions, a trunkindicating device at said first position, a line indicating device atsaid second position, means at said first position whereby an operatorreceives the designation of wanted lines, means controlled at saidposition for initiating a connection to a wanted telephone line, meansresponsive thereto for selecting.

an idle trunk to said second operators position and for causing saidtrunk indicating device to give the trunk indication of the selectedtrunk line at said first operators position, a circuit for connectingthe calling line and the selected trunk, means controlled at said iirstposition for causing said line indicating device to give the designationof the wanted line, and a manual switch by means of which an operator atsaid second position connects the selected trunk to the wanted telephoneline.

2. In a telephone system, a plurality of operators positions, eachprovided with a numerical key set, a plurality of senders common to saidpositions, means for allotting senders for use, means controlled at anoperators position for associating its numerical key set with anallotted sender whereby said sender is variably adjusted in accordancewith a predetermined code, other operators positions each provided withan indicating device, and means under the control of a sender foroperating an indicating device in accordance with the adjustment of saidsender.

3. In a telephone s stem, a plurality of oiiices, la plurality o trunkcircuits connecting one oice with a second oiiice, a plurality ofsenders at said first oHice, means for preselecting a sender for useahead of the call, a plurality of switches, a link circuit terminatingat one end in a switch for selecting a trunk circuit and terminating atits other end in a switch for seizing a preselected sender, a thirdswitch for seizing an idlelink circuit, means for variably `adjusting aselected sender, and means for transmitting impulses through said firstand second mentioned switches to the selected trunk.

4. In a telephone offices, trunk circuits connecting one oice with asecond olice, a plurality of Senders, means for preselecting a senderJfor use ahead of the call, a plurality of switches, means for variablyadjusting a preselected sender in accordance with a predetermined code,a link circuit terminating at one end in a switch operating to seize atrunk circuit, said link circuit terminating at its other end in aswitch for seizing a preselected sender, a third switch for seizing anidle link circuit and thereby eiect the operation of said irst andsecondswitches, an indicating device at the second oiiice, and meanscontrolled by said adjusted sender and controlled through said first andsecond switches over a selected trunk for selectively operating saidindicating device.

v5. The methodof completing a telephone connection which consists in thesubscriber repeating the number of the wanted line to system, aplurality of an operator, said operator thereupon man- Aually selectingthe oiiice through which a wanted subscriber can be reached, selecting atrunk to said oiiice, visually signallingthe designation of the selectedtrunk to said o erator, said operator then connect-ing tiie callingsubscriber and the selected trunk, visually signalling the number of thewanted subscriber to a second operator, and connecting the wanted lineto the designated trunk.

6. In a telephone system, a plurality of oiiices, an A operatorsposition at one of said oiiices, B operators positions at the otheroiiices, trunks for connecting said A operators position to each of saidother ofices, oiiice keys one for each oilice accessible to said Aoperators position, and means responsive to the operation of 'an oiicekey for automatically selecting a trunk to a wanted oiiice and forautomatically indicating the designation of said trunk to said Aoperators position.

7. In a telephone system, a plurality of telephone oilices, an Aoperators position at one of said offices` B operators positions at theother oiiices, trunks for connecting said A operators position `to saidother oiices, office keys one for each oice accessible to said Aoperators position, automatic switchmg means operating responsive to theoperation of one of said keys for automatically selecting trunks to awanted oilice, and automatic indicating means for giving the designationof selected trunks.

8. In a telephone system, a plurality of telephone oliices, a pluralityof A operators positions at one of saido ces, B operators positions ateach of said other offices, trunks leading from said A operatorspositions to each of said other ofiices, an oflice key at each Aoperators osition for each oilice reached from said A.) o eratorspositions, .a trunk indicator at said A operators positions, a numberindicator at each of said distant oices, a plurality of senders commonto said operators positions and variably adjusted therefrom, and meansresponsive to the adjustment of said senders for selectively operatingsaid number indicators.

9. In a telephone system, a number storing device comprising groups ofmarginal and sensitive relays, each group of relays serving to store thedesignation of one digit, a single set of ten numerical keys and meansfor successively and variably adjustin said groups of relays under thecontrol o said set of keys.

10. In a telephone system, operators positions each of which is providedwith a single set of ten numerical keys, a plurality of sets of numberstoring devices common to said operators ositions, means for associatingan idle set ci) number storing devices with the key set of an operatorsposition, means for successively operating said set of keys for variablyadjusting the associated set of number storing devices, and meansselectively actuated by said set of number-storing devices.

11. In a telephone system, a plurality of operators positions each ofwhich is provided with a single set of ten numerical keys, a pluralityof register senders common to said operators positions, each registersender comprising a plurality of groups of relays, means for associatingan idle register sender with the key set of an operators position, andswitching means for each register whereby the repeated operation of akey set is effective to operate a diii'erent group of relays of theassociated sender.

12. In a telephone system, a plurality of operators positions each ofwhich is provided with a single set of ten numerical keys, a pluralityof register senders common to said operators positions each registersender comprising a plurality of groups of relays of various degrees ofelectromagnetic sensitivity, means for associating an idle registersender with the key set of an operators position, and' switching meansfor each register whereby the repeated operation of a key set iseffective to operate a different group of relays of the associatedsender.

a plurality of 13. In a telephone system, two telephone ofiices, an A oerators position atA one of said offices, a operators position at theother oiiice, a register sender at the A operators position comprising agroup of registers arranged to be selective y operated under the.control of the A operator, a progressively movable switch associatedwith said register sender, an indicating device at the B operatorsposition, a progressively movable switch associated therewith, and meansfor operating said switches alternately whereby the registration on saidrevister sender is transferred'to the indicating device at the Boperatorsposition.

14. In a telephone system, an A operators position, a register senderincluding a progressively movable switch' located at said position,means at said position for variably adjusting said register sender inaccordance with a predetermined code, a B operators position, a trunkcircuit connecting said operators positions, an indicator at said Boperators position arranged to be variably operated in accordance withthe settingof said register sender,a progressively movable' switchassociated with said indicator, means for settin said switches inoperation, means effective t ereafter whereby the switch associated withsaid indicator completes operating circuits for the switch associatedwith said' register sender and means whereby the switch associated withthe register sender closes operating circuits for the switch associatedwith said indicator, and means functioning during the advance of saidswitches for effecting the operation of the indicator in accordance withthe adjustment of said register sender.

l5. In a telephone system, a plurality of offices, a plurality of Aoperators positions at one of said oilices, a B operators position atthe other oilice, a plurality of register senders for the use of said Aoperators positions arranged to be variably adjusted therefrom, meansfor associating an idle register sender with an A operators position,each of said register senders bein provided with a progressively movablesen er switch, a trunk circuit connecting said A operators positions andsaid B operators position, an indicating device located at said Boperators position and a progressively movable receiver switchassociated therewith, means for initiating the operation of saidswitches, other means eilective thereafter whereby the receiver switcheffects the advance of the sender switch, additional means whereby thesender switch effects the advance of said receiver switch, and meansoperating under the control of said switches whereby the register sendereffects the operation of said indicator over said trunk circuit.

16. In a telephone system, a plurality of oiiices, a plurality of Aoperators positions at one of said offices., a B operators position atthe other oiiice, a single strip of keys at each A operators posit1on, aplurality of register senders for the use of said A operators positionsand arranged to be variably adjusted by said keys, means for associatingan idle register sender with an A operators position, each of saidregister senders being provided with a progressively movable senderswitch, a trunk circuit connecting said A operators positionsand said Boperators position, an indicating device located at said B operatorsposition, a'progressively movable receiver switch associated therewith,means for initiating the operation .otiices, a plurality of A operatorspositionsA at one of said offices, a B operators position at the otheroiiice, a plurality of register senders for the use of said A operatorspositions arranged to be variably adjusted therefrom, means associatedwithd each A operators position for preselecting an idle registersender, each of said register senders being provided with aprogressively movable sender switch, a trunkv circuit connecting said Aoperators positions and Asaid B operators position, an indicating devicelocated at said B operators position and a progressively movablereceiver switch associated therewith, means for initiating the operationof said switches, other means eective thereafter whereby the receiverswitch ei'lects the advance of the sender switch, additional meanswhereby the sender switch effects the advance of said receiver switch,and means operating under the control of said switches whereby theregister sender effects the operation of said indicator over said trunkcircuit.

18. In a telephone system, a plurality of oiiices, a plurality of Aoperators positions at one of said offices, a B operators position atthe other oiiice, a plurality of register senders for the use of said Aoperators positions, each of said register senders including a pluralityof relays arranged to be variably adjusted from said operatorspositions, means for associating an idle register sender with an Aoperators position, each of said register senders being vprovided with aprogressively movable sender switch, a trunk circuit connecting said Aoperators positions and said B operators position, an indicating devicelocated at said B operators position and a `progressively movablereceiver switch associated therewith, means for initiating the operationof said switches, other means effective thereafter whereby the receiverswitch effects the advance of the sender switch, additional meanswhereby the sender switch effects the advance of said receiver switch,and means operating under the control of said switches whereby theregister sender effects the operation of said indicator over said trunkcircuit.

19h. In a telephone system, a plurality of operators positions, each ofsaid positions being provided with a single set of keys, a plurality ofnumber storing devices for the common use or' saidpositions and arrangedto be variably adjusted in accordance with the operation of said keyset, and a progressively movable preselector switch for each operatorsposition for associating the key set of that position with an idleregister \sende r.

20. In a telephone system, a plurality of operators positions, each ofsaid positions being provided with a single strip of keys, a pluralityof senders common to said operators positions, each sender having aplurality of registers arranged to be'successively operated by therepeated actuation of a strip of keys.

21. In a telephone system, an A operators position, a B operatorsposition, telephone lines terminating at each of said positions, a trunkcircuit extending between said posi tions, a register sender in said Aoperators position arranged to be variably actuated 1n accordance withthe designation of a wanted telephone line, an indicating device at saidB operators position, and means having a signaling circuit including atleast one of the conductors of said trunk circuit for transferring thedesignation recorded -on said register sender to said indicating device,

said means including mechanism for reversing the direction of currentflow in said signaling circuit a plurality of timesduring the transferof the designation from said register sender to said indicating device.

22. In a telephone system, an A operators position, a B operatorsposition, telephone lines terminating in said positions, a trunk circuitextending between said positions, a register sender at said A operatorsposition arranged to be actuated in accordance with the designation of awanted telephone line, an indicating device at said B operatorsposition, a signaling circuit including at least one conductor of saidtrunk circuit for transerring the designation -of said register senderto said indicating device, meansat said B operators position forconnecting said trunk circuit to the indicated line, and two means forreleasing said register sender and said receiving device prior to thetermination of the connection.

22. In a telephone system, an A operators osition, a B. operatorsposition,l telephone ines terminating at each of said positions,

a registering device located at said A operators position and arrangedto be actuated in accordance with the designation of a wanted telephoneline, an indicating device located at said B operators position, asignaling circuit including at least one conductor of said trunk circuitfor transferring the designation of said wanted telephone line from saidregistering device to said indicating device, a release key, andswitching means for connecting said trunk circuit to said wantedtelephone line, said release and indicating devices.

In witness whereof, I hereunto subscribe my name this 2nd day ofDecember A. D.

WINFRED T. POWELL.

